1. Field of the Invention
The present invention relates to integrated circuits. More particularly, the present invention relates to a method and apparatus for determining if a signal has transitioned to a new logic state.
2. The Background Art
Signals used in digital electronics are typically characterized by whether they are high (a binary "1"), or low (a binary "0"). In addition to knowing whether a signal is high or low, it is also important to know when a signal has made a transition from high to low, or from low to high.
As higher speed electronics has been developed, the effects of noise on the operation of digital circuits have become more pronounced. This is because modern digital circuits respond to higher frequency signals than in the past. As a result, the bandwidth of the circuits has increased, thus allowing more signal noise to affect circuit operation. Bad effects can be seen, for instance, when a noise spike is incorrectly determined by electronic circuitry to be a transition from low to high, or from high to low.
A noise spike which is incorrectly determined by a microprocessor to be an interrupt can cause a number of things to occur. At best, the interrupt may cause the system containing the microprocessor to operate less efficiently than otherwise would be seen. At worst, a false interrupt could cause the system to reset during a critical time period, thus causing the loss of data, the loss of operation of the system, or other catastrophic effects. It would therefore be beneficial to provide a method and apparatus which detects signal transitions from one state to another, with significantly reduced errors caused by system noise.
For conventional, non-microprocessor based circuits, a noise spike may cause anything from an undesired latch state, to circuit faults which require reinitialization of the entire system. It would therefore be beneficial to provide a method and apparatus which could be included in systems having conventional integrated circuits, and would have significantly reduced errors resulting from system noise.